In general, in a vehicle such as an automobile or the like, the electric connection box such as a junction box, a fuse box, a relays-box or the like has been used for receiving electric parts such as wire harness connecting parts, a fuse, relays, an electronic control unit, or the like.
Since the electric connection box is mostly located in an engine compartment or a lower side part of a vehicle body, in such cases that it heavily rains, the vehicle body is washed by the water under the high pressure, and the practical test such as a pool diving test is executed, the water can penetrates through to the inside of the electric connection box. Furthermore, there can be dew condensation and collection of water drops inside the electric connection box. In such cases that the water penetrates through or collects inside the electric connection box, there are risks that such parts as circuit are short-circuited and that electrical current leaks, and, accordingly, the above described water may causes malfunction of the operation and melting to damage the parts.
Therefore, when the electric connection box has a lower case or lower cover, there is applied the structure in which a water discharging hole is formed on the bottom wall of the lower cover for draining off water which is inside the electric connection box to the outside through the water discharging hole in order to prevent water from collecting inside the electric connection box and to prevent water from penetrating through from the outside.
FIG. 3 is cross sectional view for explaining one example of the conventional drain structure of the electric connection box.
As shown in FIG. 3, the conventional drain structure of the electric connection box K2 includes the hollow drain portion 52 which is continuous with the water discharging hole 51 formed on the bottom wall 50 of the lower case or lower cover of the electric connection box.
The bottom wall 50 of the electric connection box is formed to downwardly incline toward the water discharging hole 51.
The drain portion 52 has an upper surface 52a and a bottom surface 52b. A communication hole 52c which is continuous with lower part of the water discharging hole 51 is formed on the upper surface 52a. A through hole 52d for passing through the water which penetrates from the outside is formed in one edge part of the upper surface 52a and bottom surface 52b. A drain port 52e for draining off the water which penetrates from the outside and which penetrates through the water discharging hole 51 to the outside is formed in another edge part of the upper surface 52a and bottom surface 52b. 
The drain port 52e has vertical width greater than the through hole 52d. The bottom wall 52b of the drain portion 52 is formed to incline downward from the through hole 52d toward the drain port 52e. 
In the conventional drain structure of electric connection box K2, the water penetrating through to the inside of the electric connection box drops on the bottom wall 50, collects on the water discharging hole 51 along the inclination, passes through the communication hole 52c of the drain portion 52, and is drained off from the drain port 52e to the outside (arrow M1).
On the other hand, since the water which upwardly penetrates from the outside is dammed by the outer wall of the drain portion 52, it is possible to prevent the water from penetrating through to the inside of the electric connection box (arrow M2).
The water which penetrates from the outside through the through hole 52d is drained off along the bottom surface 52b of the drain portion 52 and through the drain port 52e to the outside (arrow M3).
Furthermore, the water which penetrates through the drain port 52e is brought back along the bottom surface 52b of the drain portion 52 and drained off through the drain port 52e to the outside (arrow M4) (hereinafter, this art is referred to as prior art 1).
And in Patent document 1, there is proposed the drain structure of the electric connection box including a substantially funnel-shaped portion which is provided on a bottom wall of the electric connection box and whose base edge part is narrowed as going downward, a drain port including a cylindrical portion whose edge portion continuous with the substantially funnel-shaped portion has the same inner shape as the inner shape of a lowermost edge portion of the substantially funnel-shaped portion, and a reflecting member provided in the substantially funnel-shaped portion of the drain port, wherein the reflecting member includes a mortar-shaped recess portion which has a hole opening downward and is widen as going downward and a fixed flange portion which is fixed on the substantially funnel-shaped portion, and wherein a discharging portion through which moister inside the electric connection box can be discharged to the outside of the electric connection box, is provided on the fixed flange portion (hereinafter, this art is referred to as prior art 2).
Furthermore, in Patent document 2, there is proposed the drain structure of the electric connection box in which a drain port wall is provided to be projected from a case bottom wall of the electric connection box and a pair of waterproof lid engaging portions is provided to be faced each other and to be projected from the lower edge of the drain port wall, an engaging hook is inwardly provided to be projected from the lower edge of the waterproof engaging portion, the waterproof lid is mounted with the both edges held by the engaging hooks, and the waterproof lid is lifted up by water pressure from below and seals an opening of the lower edge of the drain port wall (hereinafter, this art is referred to as prior art 3).
Patent document 1: Japanese Patent Application Publication No. 2006-67709
Patent document 2: Japanese Patent Publication No. 3052807